GameServer is a sophisticated, game server designed for online games
A fun realistic multiplayer free-and-open-source first-person-shooter!
oGame-like browser space realtime strategy game based on xNova
Updated client for Battletech MUX game servers
Pinewood Derby Race Management
starrydb is game server engine
web cms for clans and esport related pages
MultiVice - is a fully customizable multiplayer modification for Grand
A MMORPG Engine, written in PhP and SQL
Open Source Virtual World and MMOG Development Platform
A open-source online football manager like hattrick
LetsPlay is a bukkit plugin.